Use any type in a function parameter in C++

Question

I am trying to find a way to get this function into a more generic one.

  void addStage(Image (f)(Image));

The thing i want to get is something that can recieve different types of functions with or without parameters, void or not.

I have tried something like this but of course it is not working.

void addStage(auto (f)(auto));

For giving more context I will say that this functions are going to be stages from a pipeline.

Answer 1

template <typename AnyFunction>
void addStage(AnyFunction f) {
  // implement in header file!
}

Answer 2

Use SFINAE:

template<class T>
std::enable_if_t<std::is_function_v<T>, void> addStage(T* f) {
    ...
}

But, if you don't need any special check (wether T is a function or no) you can actually just use a template and leave to the compiler all the checks:

template<class T>
void addStage(T f) {
   ...
}